I got this error when the leader of a LFG party I joined enabled party sync (after I accepted the sync). Got the same error again a few seconds after sync, and it might have kept continuing but the party was disbanded at that point.

2x ExtraQuestButton\Utils.lua:130: attempt to index local 'info' (a nil value)
[string "@ExtraQuestButton\Utils.lua"]:130: in function GetClosestQuestItem' [string "@ExtraQuestButton\ExtraQuestButton-90000.21-Release.lua"]:150: in function callback'
[string "@ExtraQuestButton\mixins\EventHandlerMixin.lua"]:56: in function <ExtraQuestButton\mixins\EventHandlerMixin.lua:53>

Locals:
self =

{
GenerateItemLinkFromID = defined @ExtraQuestButton\Utils.lua:165
mixins = {
}
Print = defined @ExtraQuestButton\Utils.lua:173
GetCurrentMapID = defined @ExtraQuestButton\Utils.lua:169
GetClosestQuestItem = defined @ExtraQuestButton\Utils.lua:94
db = {
}
GetNPCID = defined @ExtraQuestButton\Utils.lua:152
L = {
}
GetItemID = defined @ExtraQuestButton\Utils.lua:161
itemData = {
}
}
closestQuestItemLink = nil
closestDistance = 1000
onlyInZone = false
onlyIfWatched = false
(for index) = 2
(for limit) = 62
(for step) = 1
index = 2
info = nil
(*temporary) = nil
(*temporary) = 2
(*temporary) = nil
(*temporary) = "attempt to index local 'info' (a nil value)"
ns = {
GenerateItemLinkFromID = defined @ExtraQuestButton\Utils.lua:165
mixins = {
}
Print = defined @ExtraQuestButton\Utils.lua:173
GetCurrentMapID = defined @ExtraQuestButton\Utils.lua:169
GetClosestQuestItem = defined @ExtraQuestButton\Utils.lua:94
db = {
}
GetNPCID = defined @ExtraQuestButton\Utils.lua:152
L = {
}
GetItemID = defined @ExtraQuestButton\Utils.lua:161
itemData = {
}
}
GetQuestDistanceWithItem = defined @ExtraQuestButton\Utils.lua:18

Fixed in 78c78e3.